Astrophysics and Astronomy Commons^™

Characterization Of Optical Constants For Uranium From 10 To 47 Nm, Nicole Brimhall, Nicholas Herrick, David D. Allred, R. Steven Turley, Michael Ware, Justin Peatross

Faculty Publications

We use a laser high-harmonics-based extreme-ultraviolet (EUV) polarimeter to determine the optical constants of elemental uranium in the wavelength range from 10 to 47 nm. The constants are extracted from the measure ratio of p-polarized to s-polarized reflectance from a thin uranium film deposited in situ. The film thickness is inferred from a spectroscopic ellipsometry measurement of the sample after complete oxidation in room air. Uranium has been used as a high-reflectance material in the EUV. However, difficulties with oxidation prevented its careful characterization previous to this study. We find that measured optical constants for uranium vary significantly from previous …

Hr 7355 - Another Rapidly Braking He-Strong Cp Star?, Zdeněk Mikulášek, Jiří Krtička, Gregory W. Henry, S. N. De Villiers, Ernst Paunzen, Miloslav Zejda

Information Systems and Engineering Management Research Publications

Context. Strong meridional mixing induced by rapid rotation is one reason why all hot main-sequence stars are not chemically peculiar. However, the finding that the He-strong CP star HR 7355 is a rapid rotator complicates this concept.
Aims. Our goal is to explain the observed behaviour of HR 7355 based on period analysis of all available photometry.
Methods. Over two years, we acquired 114 new BV observations of HR 7355 at observatories in Arizona, U.S.A and Cape Town, South Africa. We performed period analyses of the new observations along with new analyses of 732 archival measurements from the Hipparcos and …

Development And Demonstration Of A Field-Deployable Fast Chromotomographic Imager, Daniel C. O'Dell

Theses and Dissertations

A field deployable hyperspectral imager utilizing chromotomography (CT), with a direct vision prism (DVP) as the dispersive element, has been constructed at AFIT. This research is focused on the development and demonstration of the CT imager. An overview of hyperspectral imaging, chromotomography, a synopsis of reconstruction algorithms, and other CT instruments are given. The importance of component alignment, instrument calibration, and exact prism angular position data are discussed. A simplistic \shift and add" reconstruction algorithm was utilized for this research. Although limited in its ability to reconstruct a spatially and spectrally diverse scene, the algorithm was adequate for the testing …

The M•–Σ* Relation Derived From Sphere Of Influence Arguments, Daniel P. Batcheldor

Aerospace, Physics, and Space Science Faculty Publications

The observed relation between supermassive black hole (SMBH) mass (M•) and bulge stellar velocity dispersion (σ*) is described by log M• = α + βlog(σ*/200 km s-1). As this relation has important implications for models of galaxy and SMBH formation and evolution, there continues to be great interest in adding to the M• catalog. The "sphere of influence" (ri) argument uses spatial resolution to exclude some M• estimates and pre-select additional galaxies for further SMBH studies. This Letter quantifies the effects of applying the ri argument to a population of galaxies and SMBHs that do not follow the M•–σ* relation. …

Evaluation Of Interplanetary Magnetic Field Tracing Models Using Impulsive Seps, Brian P. Elliott

Theses and Dissertations

Current Interplanetary Magnetic Field (IMF) models are evaluated in this study to determine which model(s) perform an accurate representation of this magnetic structure. These IMF models include the Parker Spiral model, the Potential Field Source Surface (PFSS) model, the Wang-Sheeley-Arge (WSA) model and the ENLIL model. Impulsive Solar Energetic Particles (SEPs) are used as tracers to determine the magnetic structure of the IMF and provide source locations for model comparisons. Each individual model is analyzed, compared to the identified solar source region and a longitude/latitude offset of these traces assigned. The model connection of the PFSS and Parker models is …

Studying The Small Scale Ism Structure With Supernovae, F. Patat, N. L. J. Cox, J. Parrent, D. Branch

Dartmouth Scholarship

In this work we explore the possibility of using the fast expansion of a Type Ia supernova photosphere to detect extra-galactic ISM column density variations on spatial scales of ∼100 AU on time scales of a few months. We constructed a simple model which describes the expansion of the photodisk and the effects of a patchy interstellar cloud on the observed equivalent width of Nai D lines. Using this model we derived the behavior of the equivalent width as a function of time, spatial scale and amplitude of the column density fluctuation

A Test Of Pre-Main-Sequence Lithium Depletion Models, Jennifer Chun Ming Yee , '07, Eric L.N. Jensen

Physics & Astronomy Faculty Works

Despite the extensive study of lithium depletion during pre-main-sequence (PMS) contraction, studies of individual stars show discrepancies between ages determined from the Hertzsprung-Russell (H-R) diagram and ages determined from lithium depletion, indicating open questions in the PMS evolutionary models. To further test these models, we present high-resolution spectra for members of the beta Pictoris Moving Group (BPMG), which is young and nearby. We measure equivalent widths of the 6707.8 angstrom Li I line in these stars and use them to determine lithium abundances. We combine the lithium abundance with the predictions of PMS evolutionary models in order to calculate a …

Central Compact Objects, Trevor Meek

Physics

Central compact objects (CCOs) are point-like sources found near the center of supernova remnants (SNRs). They emit X-rays, but show no radio or gamma ray counterpart. Typical CCO candidates have emission radii on the order of 0.2-3.0 km. This is much smaller than the typical radius of a neutron star, making CCOs a difficult astronomical phenomenon to identify.

Optical/Infrared Observations Of The X-Ray Burster Ks1731-260 In Quiescence, C. Zurita, E. Kuulkers, R. M. Bandyopadhyay, E. M. Cackett, P. J. Groot, J. A. Orosz, M. A. P. Torres, R. Wijnands

Physics and Astronomy Faculty Research Publications

Aims. We performed an optical/infrared study of the counterpart of the low-mass X-ray binary KS 1731–260 to test its identification and obtain information about the donor.

Methods. Optical and infrared images of the counterpart of KS 1731–260 were taken in two different epochs (2001 and 2007) after the source returned to quiescence in X-rays. We compared these observations with those obtained when KS 1731–260 was still active.

Results. We confirm the identification of KS 1731–260 with the previously proposed counterpart and improve its position to α = 17:34:13.46 and δ = -26:05:18.60. The H-band magnitude of this …

Radio Emission From Substellar Companions Of Evolved Cool Stars., Richard Ignace, Mark Giroux, Donald Luttermoser

ETSU Faculty Works

A number of substellar companions to evolved cool stars have now been reported. Cool giants are distinct from their progenitor main-sequence low-mass stars in a number of ways. First, the mass loss rates of cool giant stars are orders of magnitude greater than for the late-type main-sequence stars. Secondly, on the cool side of the Linsky–Haisch ‘dividing line’, K and M giant stars are not X-ray sources, although they do show evidence for chromospheres. As a result, cool star winds are largely neutral for those spectral types, suggesting that planetary or brown dwarf magnetospheres will not be effective in standing …

High-Energy Amplitudes In N= 4 Sym In The Next-To-Leading Order, Ian Balitsky, Giovanni A. Chirilli

Physics Faculty Publications

The high-energy behavior of the N = 4 SYM amplitudes in the Regge limit can be calculated order by order in perturbation theory using the high-energy operator expansion in Wilson lines. At large Nc , a typical four-point amplitude is determined by a single BFKL pomeron. The conformal structure of the four-point amplitude is fixed in terms of two functions: pomeron intercept and the coefficient function in front of the pomeron (the product of two residues). The pomeron intercept is universal while the coefficient function depends on the correlator in question. The intercept is known in the first two orders …

Solar Eclipse Monitoring For Solar Energy Applications Using The Solar And Moon Position Algorithms, Ibrahim Reda

Publications (E)

This report includes a procedure for implementing an algorithm (described by Jean Meeus [1]) to calculate the Moon’s zenith angle with uncertainty of ±0.001° and azimuth angle with uncertainty of ±0.003°. The step-by-step format presented here simplifies the complicated steps Meeus describes to calculate the Moon’s position, and focuses on the Moon instead of the planets and stars. It also introduces some changes to accommodate for solar radiation applications. These include changing the direction of measuring azimuth angles from north and eastward instead of from south and eastward, and the direction of measuring the observer’s geographical longitude to be measured …

The Equivalence Principle, Uniformly Accelerated Reference Frames, And The Uniform Gravitational Field, Gerardo Muñoz, Preston Jones

Publications

The relation between uniformly accelerated reference frames in flat spacetime and the uniform gravitational field is examined in a relativistic context. It is shown that contrary to previous statements, equivalence does not break down in this context. No restrictions to Newtonian approximations or small enclosures are necessary.

On The Anomalous Balmer Line Strengths In Globular Clusters, Violet Poole, Guy Worthey, Hyun Chul Lee, Jedidiah Serven

Physics & Astronomy Faculty Publications

Spectral feature index diagrams with integrated globular clusters and simple stellar population models often show that some clusters have weak Hβ, so weak that even the oldest models cannot match the observed feature depths. In this work, we rule out the possibility that abundance mixture effects are responsible for the weak indices unless such changes operate to cool the entire isochrone. We discuss this result in the context of other explanations, including horizontal branch morphology, blue straggler populations, and nebular or stellar emission fill-in, finding a preference for flaring in M giants as an explanation for the Hβ anomaly. © …

Core Gas Sloshing In Abell 1644, Ryan E. Johnson, Maxim Markevitch, Gary A. Wegner, Christine Jones, William R. Forman

Dartmouth Scholarship

We present an analysis of a 72 ks Chandra observation of the double cluster Abell 1644 (z = 0.047). The X-ray temperatures indicate that the masses are M ₅₀₀ = (2.6 ± 0.4) × 10¹⁴ h ^–1 M _☉ for the northern sub-cluster and M ₅₀₀ = (3.1 ± 0.4) × 10¹⁴ h ^–1 M _☉ for the southern, main cluster. We identify a sharp edge in the radial X-ray surface brightness of the main cluster, which we find to be a cold front, with a jump in temperature of a factor of ~3. This edge possesses …

Infrared Spectroscopy Of Symbiotic Stars. Viii. Orbits For Three S-Type Systems: Ae Arae, Y Coronae Australis, And Ss 73-147, Francis C. Fekel, Kenneth H. Hinkle, Richard R. Joyce, Peter R. Wood

Information Systems and Engineering Management Research Publications

With new infrared radial velocities we have computed orbits of the M giants in three southern S-type symbiotic systems. AE Ara and SS 73-147 have circular orbits with periods of 803 and 820 days, respectively. The eccentric orbit of Y CrA has a period that is about twice as long, 1619 days. Except for CH Cyg it is currently the S-type symbiotic system with the longest period for which a spectroscopic orbit has been determined. The Paschen δ emission line velocities of AE Ara are nearly in antiphase with the M giant absorption feature velocities and result in a mass …

High-Excitation Emission Lines Near Eta Carinae, And Its Likely Companion Star, Andrea Mehner, Kris Davidson, Gary J. Ferland, Roberta M. Humphreys

Physics and Astronomy Faculty Publications

In order to study the distribution of gas and ionizing radiation around η Car and their implications for its likely companion star, we have examined high-excitation emission lines of [Ne III], [Fe III], etc., in spectra obtained with the Hubble Space Telescope/Space Telescope Imaging Spectrograph instrument during 1998-2004. Our principal results, some of them unexpected, are as follows. (1) The high-excitation fluxes varied systematically and non-trivially throughout η Car's 5.5 year spectroscopic cycle. Instead of rising to a plateau after the 1998 ''event,'' they changed continuously with a maximum in mid-cycle. (2) At one significant location a brief, strong …

An Analytical And Numerical Treatment Of The Carter Constant For Inclined Elliptical Orbits About A Massive Kerr Black Hole, Peter Komorowski, Sree Ram Valluri, Martin Houde

WORLDiscoveries Research Showcase

In an extreme binary black hole system, an orbit will increase its angle of inclination (i) as it evolves in Kerr spacetime. We focus our attention on the behaviour of the Carter constant (Q) for near-polar orbits. The value of Q for bound orbits is non-negative; and an increase in Q corresponds to an increase in i. For a Schwarzschild black hole, the polar orbit represents the boundary between the prograde and retrograde orbits at which Q is at its maximum value. The introduction of spin (S = |J|/M2) to the massive black hole causes this boundary, or Abutment, to …

Recent Discoveries Of Supersoft X-Ray Sources In M 31, M. Henze, W. Pietsch, E. Haberl, G. Sala, M. Hernanz, D. Hartzidimitriou, A. Rau, Dieter H. Hartmann, J. Greiner, M. Orio, H Stiele, M.J. Freyberg

Publications

Classical novae (CNe) have recently been reported to represent the major class of supersoft X-ray sources (SSSs) in the central area of our neighbouring galaxy M 31. This paper presents a review of results from recent X-ray observations of M 31 with XMM-Newton and Chandra. We carried out a dedicated optical and X-ray monitoring program of CNe and SSSs in the central area of M 31. We discovered the first SSSs in M 31 globular clusters (GCs) and their connection to the very first discovered CN in a M 31 GC. This result may have an impact on the CN …

Constraining The Black Hole Mass Spectrum With Gravitational Wave Observations – I. The Error Kernel, Danny C. Jacobs, Joseph E. Plowman, Ronald W. Hellings, Sachiko Tsuruta, Shane L. Larson

All Physics Faculty Publications

Many scenarios have been proposed for the origin of the supermassive black holes (SMBHs) that are found in the centres of most galaxies. Many of these formation scenarios predict a high-redshift population of intermediate-mass black holes (IMBHs), with masses M_• in the range 10²≲M_•≲ 10⁵ M_⊙. A powerful way to observe these IMBHs is via gravitational waves the black holes emit as they merge. The statistics of the observed black hole population should, in principle, allow us to discriminate between competing astrophysical scenarios for the origin and formation of SMBHs. However, …

Dynamics Of Strong Radio Sources With Umrt-Ii., Mohammed Awid Al-Amri

Student Works (2010-2019)

Radio astronomy is a new field in Southeast Asia. University Malaya Radio Telescope UMRT-II is located on the roof of Block B in the Department of Physics, University of Malaya to detect neutral hydrogen emission line. Doppler shift of 1420.4 MHz for different radio sources were observed to determine their dynamics. By measuring the Doppler shift, the velocity V, of each radio source can be determined. Hence the dynamic of radio source can be deduced. The radio spectrum of Coma Cluster was also analyzed and its dark matter content was estimated. The observation time effort was investigated for Coma Cluster …

Gamma-Ray Spectroscopy: Meteorite Samples And The Search For 98tc, Kristopher L. Merolla

Physics

The focus of this project is low-count-level gamma-ray spectroscopy on meteorite samples in search of a particular isotope of Technetium (98Tc), which according to stellar theory, should be present in the universe. The spectral lines for 99Tc have, however, been observed in S-, M-, and N- type stars, which makes finding 98Tc created naturally a possibility, and thus a search can be justified.

Starships & The Physics Of Interstellar Travel, Shane L. Larson

Public Talks

No abstract provided.

Connections To The Cosmos: The Search For Life Beyond Earth, Shane L. Larson

Public Talks

No abstract provided.

The California Planet Survey. Ii. A Saturn-Mass Planet Orbiting The M Dwarf Gl 6491, John Asher Johnson, Andrew W. Howard, Geoffrey W. Marcy, Brendan P. Bowler, Gregory W. Henry, Debra A. Fischer, Kevin Apps, Howard Isaacson, Jason T. Wright

Information Systems and Engineering Management Research Publications

We report precise Doppler measurements of the nearby (d = 10.34 pc) M dwarf Gl 649 that reveal the presence of a planet with a minimum mass M_P sin i = 0.328 M_Jup in an eccentric (e = 0.30), 598.3 day orbit. Our photometric monitoring reveals Gl 649 to be a new variable star with brightness changes on both rotational and decadal timescales. However, neither of these timescales are consistent with the 600 day Doppler signal and so provide strong support for planetary reflex motion as the best interpretation of the observed radial velocity variations. Gl …

Chasing Cosmic Bullets: The Pierre Auger Experiment, Angela Olinto

IMSA Great Minds Program ®

The most energetic particles in the universe are ultra-high energy cosmic rays. Millions of times more powerful than anything produced by man-made accelerators, their origin has been a mystery for about a century. Over the last several years, an international collaboration of 18 countries joined forces to solve this mystery by building the Pierre Auger Observatory. Spread over 3,000 square kilometers in western Argentina, the observatory was recently inaugurated. During its construction, the observatory gathered enough of these rare particles to find the first clues to their origin. The most energetic of these particles tend to point to cosmologically nearby …

Ordered Magnesium-Lithium Alloys: First-Principles Predictions, Richard H. Taylor, Gus L. W. Hart, Stefano Curtarolo

Faculty Publications

Magnesium-lithium (Mg-Li) alloys are among the lightest structural materials. Although considerable work has been done on the Mg-Li system, little is known regarding potential ordered phases. A first and rapid analysis of the system with the high-throughput method reveals an unexpected wealth of potentially stable low-temperature phases. Subsequent cluster expansions constructed for bcc and hcp superstructures extend the analysis and verify our high-throughput results. Of particular interest are those structures with greater than 13 at. % lithium, as they exhibit either partial or complete formation as a cubic structure. Order-disorder transition temperatures are predicted by Monte Carlo simulations to be …

Refined Stellar, Orbital And Planetary Parameters Of The Eccentric Hat-P-2 Planetary System, András Pál, Gáspár Á. Bakos, Guillermo Torres, Robert W. Noyes, Debra A. Fischer, John A. Johnson, Gregory W. Henry, R. Paul Butler, Geoffrey W. Marcy, Andrew W. Howard, Brigitta Sipőcz, David W. Latham, Gilbert A. Esquerdo

Information Systems and Engineering Management Research Publications

We present refined parameters for the extrasolar planetary system HAT-P-2 (also known as HD 147506), based on new radial velocity and photometric data. HAT-P-2b is a transiting extrasolar planet that exhibits an eccentric orbit. We present a detailed analysis of the planetary and stellar parameters, yielding consistent results for the mass and radius of the star, better constraints on the orbital eccentricity and refined planetary parameters. The improved parameters for the host star are M★= 1.36 ± 0.04 M⊙ and R★= 1.64 ± 0.08 R⊙, while the planet has a mass of Mp= 9.09 ± 0.24 MJup and radius of …

Simulating The Fticr-Ms Signal Of A Decaying Beryllium-7 Ion Plasma In A 2d Electrostatic Pic Code, Michael Takeshi Nakata

Theses and Dissertations

Beryllium-7 (Be-7) only decays by electron capture into lithium-7 (Li-7) with a half life of 53 days. We study the effect of ionization on this decay rate. We do so by trapping a Be-7 ion plasma in a cylindrical Malmberg-Penning trap and measuring Be-7 and Li-7 concentrations as functions of time by using Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS). We have simulated these signals in a 2-dimensional electrostatic particle-in-cell (PIC) code. The two spectrum peaks merge at high ion densities whereas at low ion densities they can be resolved. The merged peak shifts linearly according to the relative …

Discovery Of Variability In The Very High Energy Gamma-Ray Emission Of 1es 1218+304 With Veritas, P. T. Reynolds, Et Al

Physical Sciences Publications

We present results from an intensive VERITAS monitoring campaign of the high-frequency peaked BL Lac object 1ES 1218+304 in 2008/2009. Although 1ES 1218+304 was detected previously by MAGIC and VERITAS at a persistent level of ~6% of the Crab Nebula flux, the new VERITAS data reveal a prominent flare reaching ~20% of the Crab. While very high energy (VHE) flares are quite common in many nearby blazars, the case of 1ES 1218+304 (redshift z = 0.182) is particularly interesting since it belongs to a group of blazars that exhibit unusually hard VHE spectra considering their redshifts. When correcting the measured …